The present invention relates to a web printing press.
Japanese Patent Laid-Open No. 2008-308341 (reference 1) proposes a conventional web printing press. The web printing press described in reference 1 will be described with reference to FIG. 5. A web printing press 201 includes a sheet feeding device 202, two printing units 204 and 205, a fixing device 206 including a thermal dryer 206a, a cooling device 207, and a folder 208.
With this arrangement, a web 203 wound in a roll is fed from the sheet feeding device 202 to the printing units 204 and 205, thereby undergoing double-sided printing. The printed web 203 is exposed to hot air from the dryer 206a in the fixing device 206, thereby drying the ink printed on the web 203. At this time, upon exposure of the web 203 to hot air, a solvent in the ink transferred onto the web 203 evaporates, so the ink fixes on the paper. After that, the web 203 is wound around cylinders 207a to 207d, which are called chill rollers and through which cooling water passes, in the cooling device 207, undergoes cutting and folding processing by the folder 208, and is delivered.
On the other hand, a sheet-fed offset printing press prints/coats on a sheet using ultraviolet curing ink/varnish. This can be done using a known printing/coating method of irradiating a printed/coated sheet with ultraviolet rays from an UV (Ultraviolet) lamp to cure ultraviolet curing ink/varnish, as described in Japanese Patent laid-Open No. 54-123305 (reference 2).
In recent years, a printing/coating method which attains both energy saving and a low environmental load has been developed. In this method, ultraviolet curing ink/varnish is cured using a light-emitting diode (LED-UV) which emits light with UV wavelengths in place of a conventional UV lamp, as disclosed in Japanese Patent Laid-Open No. 2008-307891 (reference 3).
In the web printing press disclosed in reference 1 mentioned above, printing is performed using ink called thermal evaporative drying type ink (heat-set ink), and a solvent in the printed ink is forcibly evaporated and removed by hot air using a thermal drying device to fix the ink on the web. However, a web printing press prints at a speed faster than a sheet-fed offset printing press, and therefore requires a large-sized drying device in order to reliably dry the ink. Hence, the former printing press not only requires a large space for accommodation because it has a relatively large size as a whole, but also consumes a large amount of energy to activate the drying device.
The sheet-fed offset printing press disclosed in reference 2 consumes so much energy that the environmental load cannot be reduced.
In the sheet-fed offset printing press disclosed in reference 3, because light emitted by the LED-UV has an extremely narrow wavelength range (e.g., 370 nm to 380 nm), only ink/varnish which reacts to light in this narrow wavelength range can be used as ink/varnish which cures with light from the LED-UV.